The present invention relates to the field of treatment of liquids, especially liquids being administered to the circulatory system of a human patient.
In many situations it is desired to administer a liquid into the circulatory system of a patient before, during or after a surgical operation. Thus, it is known to administer a cardioplegia solution to the coronary arteries in order to arrest the heart so that open heart surgery can be performed. The administered cardioplegia solution should be cold (e.g. from about 10.degree. to 15.degree. C.) so that it also serves to cool, and thereby reduce the metabolic requirements of, the patient's heart tissue. The cardioplegia solution may be beneficially administered in admixture with the patient's whole blood in order to supply oxygen and nutrients to the heart tissue along with the cardioplegia solution.
It is known to include a heat exchanger in the cardioplegia solution (or blood/cardioplegia solution) delivery line for cooling purposes. However, the known heat exchangers used for this purpose generally suffer from one or more of the disadvantages of a non-compact size and shape, an undesirably large priming volume, an undesirably low heat exchange capacity and/or efficiency, an inadequate capability to remove any gas bubbles present in the treated liquid inlet stream, an excessive treated liquid pressure drop across the device, a tendency to significantly damage blood constituents in the treated liquid, or a propensity to form gas bubbles in the treated liquid flow regions during priming of the heat exchanger (caused for example by splashing of priming liquid within unfilled treated liquid flow channels) that might be carried through the device outlet to the patient. It is of course vitally important to remove any gas bubbles in the treated liquid inlet stream as well as to avoid the formation within the device of gas bubbles in the priming liquid during priming and in the treated liquid during subsequent operation because of the potentially disastrous consequences of introducing gas bubbles into a patient's circulatory system.